A scroll compressor for use in an air conditioner has a construction as shown in FIG. 8 where a compressor section 8 is integrated with an electric motor section 7 composed of a casing body 1, a stator 2, a rotor 3, a rotary shaft 4, an upper bearing 5, and a lower bearing 6. In the electric motor section 7, the stator 2 is fixed inside the cylindrical casing body 1 by shrink fitting or a similar method. The rotor 3 is inserted in the stator 2 with a specified gap being formed between the rotor 3 and the stator 2. The rotor 3 is fixed around the rotary shaft 4 which serves as a crankshaft by press fitting the rotor 3 to the rotary shaft 4. The upper bearing 5 and the lower bearing 6 are mounted in both end portions of the casing body 1 while rotatably supporting the rotary shaft 4.
The electric motor section 7 of such a scroll compressor is assembled normally according to a procedure as shown in FIG. 9. The casing body 1 in which the stator 2 has been inserted is vertically inverted, and the upper bearing 5 is fixed into a lower end portion of the casing body 1 by welding. The rotary shaft 4 around which the rotor 3 has been mounted is inserted into a center portion of the casing body 1 with a lower end portion of the rotary shaft 4 inserted into the upper bearing 5. The lower bearing 6 is inserted into an upper end portion of the casing body 1 with an upper end portion of the rotary shaft 4 inserted into the lower bearing 6, and the lower bearing 6 is fixed by welding. The upper bearing 5 and the lower bearing 6 are both mounted to the casing body 1 with the inner peripheral surface of the casing body 1 used as a reference surface for positioning.
According to the assembling procedure described above, when the casing body is formed in a complete cylinder shape, the centers of the bearings 5 and 6 coincide with the center of the casing body 1 to achieve an even gap between the stator 2 and the rotor 3. However, the method of producing the casing body 1 has been simplified for cost reduction in a recent scroll compressor. The casing body 1 may be produced by rolling a flat plate into a cylindrical shape. The casing body 1 thus produced has a degraded dimensional accuracy. When the bearings 5 and 6 are directly mounted to the casing body 1, the centers of the bearings 5 and 6 are displaced from the center of the stator 2, which results in an uneven gap between the stator 2 and the rotor 3 to significantly reduce the performance of the electric motor. Therefore, it is impossible to use a casing body 1 having low dimensional accuracy, which has been a cause of hampering the cost reduction of the scroll compressor.